Thermochromic properties of VO2 films made by RF-sputtering

Abstract

Vanadium dioxide films with nano-structured grains have been prepared by RF- sputtering followed by thermal annealing in low oxygen pressure. The submicro-structured crystalline grains with the size of 200 to 250 nm were revealed by FE-SEM micrographs. XRD analysis proves the monoclinic lattice of the VO2 crystalline structure and the size of the grains determined from XRD also consists of about 200 nm. The temperature of the semicoductor-to- metal phase transition (SMPT) of the films was found at tc = 64 o C. At temperatures higher than tc the resistance of the films decreased three orders in magnitude, and the transmittance at l = 1550 nm lowered from 55% to a value as low as 30%. From these thermochromic properties of VO2 films one can suggest a practical application in production of thermo-optical sensors that can be used for monitoring temperature change in petrol and/or toxic chemical storages.